Need Help in Database Design

I am indulged in developing Online Issue Tracking sytem.For that I have met with a problem in Database creation.

The Sceneario is "The Database should be specific for each and every group of customers,For example initially A is a company with 10 users accessing the product after two days B is a company with 50 user accessing the same product".In this case the datase base should be provided to the two companies separately to maintain their transaction. How to handle this.